Controllable pitch-change mechanism for dual rotation propellers



Jan. 16', 1945. 'H M MCCOY 2,367,230

CONTROLLABLE PITCH-CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS- FiledDec. 9. 1943 INVENTOR Hon/Ago /7. MC 601 Patented Jan. 16, 1945CONTROLLABLE LERS aasy zao PITCH-CHANGE MECHA- .NISM FOR DUAL. ROTATIONPROPEL- 7 "Howard M. McCoy, Fairfield, Ohio Application December 9,1943,Serial No. 513,611

9 Claims. (c1. 170135.6)

(Granted under the act of March 3,1883, as amended April 30, 192 38; 370O. G. 757) The invention described herein may be manufacturedv and usedby or for the Government for governmental purposes,. without the paymentto me of any royalty thereon. v

This invention relates to dual rotation pro pellers and moreparticularly to mechanism for controlling the pitch of the blades ofboth of the propellers simultaneously.

' By dual rotation is commonly meant a pair of I oppositely rotatingpropellers operating in close tandem, mounted on'concentric shafts androtating at equal speeds. r

Mechanism for accomplishing this purpose as heretofore proposed iscomplicated and costly, and D it is. therefore an objectof thisinvention to provide a device which will have less parts and thereforebe of lighter weight and greater simplicity.

- the worm 24 is rotated to' turn the blades 22 in a Ithas been foundthat, in a device of this char- I acter, itis advantageous, in order tocancel propeller. torque effects, to have an arbitrary and variabledifierential pitch setting between the front and rear propeller blades.For pitch, settings used at take-off and low forward velocities thereshould be but very little if any-difference.

At high forward velocities there'should be sev-.

eral degrees difference with the setting ,of the rear propeller lowerthan that of the front. It is desirable to' have the pitch differentialvary directly between the small differential at low velocities to thelarge differential at high velocities.

Fig. l is a longitudinal axial section through a dual rotation.propeller constructed according to subject invention, the view beingmore or less schematic.

Figs. 2 and 3 are transverse sections taken at 2-2 and 3 --3, showingthe arrangement of the" gearing.

Like reference characters refer to like parts throughout the drawing.

The dual rotation propeller, which is selected as an illustrativeembodiment of this invention-,-

comprises an outboard or front propeller hub l0, whichis fast on a shaftII and is rotatable clockwise, as indicated by the arrow l2, andaninboard, or rear propeller hub I4, rotatable on the sleeve portion ofthe hub l4 anticlockwise, as indicated by the arrow l6. I Y When theterms clockwise or "anticlockwise" are hereinafter employed they shallbe intended to mean clockwise or anticlockwise when viewed from right toleft in the drawing. The relatively heavy gearing required forconnecting the front and rear hubs to each other and tothe engine,

- for opposite rotation, isvnot shown.

ID, the blades l8 are rotatable about their axes by the worm 26,

while similar blades 22 are carried on the rear hub Supported onthefront hub l4 and are rotatable about their axes .by the worm 24. Worms20 and 24, in the instant embodiment, are both right hand.

A relatively light weight gear-set 26, which, for convenience indescription, maybe referred-to as the dual rotation gear set,'isprovided for drivably connecting the worms 2!] and 24 to each other,this gearing being so arranged that when pitch increasing direction, asindicated by the arrow v28 or 30, the worm 20 will be rotated to turnthe blades It in a-pitch increasing direction, as indicated by the arrow32 or 34, the same result being achieved whether the hubs l0 and I4 arestationaryor are in a state of opposite rotation about the axis of the'hubs l0 and I4.

The gear-set 26 includes a cylindrical member 36 which is freelyrotatable on a sleeve portion 38 of the rear hub l4, and. comprisesintegrally an external gear 46 and an internal gear 42, a secondinternal gear 44 integral with the rear .hub l4, a pair of drivablyjoined sun gears 46 and 41 freely rotatable on a portion of the front.hub In, two

planet pinions 48 and 50 meshing respectively I with the internal gears42 and 44 and the drivably connected sunfgears 46- and 41, and twoplanet pinion carriers 52 and 54 for respectively rotating the planetpinions 48 and '50 on their axes while revolving them around the sungears 46 and 41 and within the ring gears 42 and 44. 7 Carrier 52 isfast on-a portion of the hub III while carrier 54 is freely rotatablethereon. Carrier 64 has an external gear 56 integral. Pinions 58 and 60drivably connect the gear-set 26 to the worms 2!) and 24, respectively,whereby rotation of the worm 24 rotates the worm 2D equally butoppositely whether the hubs l0 and I4 are stationary or are rotatingoppositely. Where it is desirable 1 that pitch change of the rearpropeller blades 22, through a given angle, cause. pitch change of thefront propeller blades l8 through a slightly greater angle, this may beaccomplished by changing the ratios between certain of the gears,

for instance, by adding one or more teeth to the gear 56 and subtractingone or more from the pinv ion 58. In'such case the gears should be setso that both propellers come to zero pitch at the same time, whereby thehigher the pitch the more pitch difference will be had between the twopropellers.

Gears 5 and 55 are part of a gear mechanism for rotating the worm 24 ofthe rear propeller for initiating pitch change, but since this mechanismforms no part of subject invention, it is not herein further shown ordescribed. The system herein shown for connecting the two parts of adual rotation propeller for unitary blade adjustment is shown anddescribed, but not claimed, in my copending application Serial No.511,935, filed November 27, 1943.

The operation of the mechanism shown and described is substantially asfollows:

Let it be assumed that the front hub I0 is rotating clockwise and therear hub l4 anticlockwise, both at'the same speed, and that, for thetime being, no pitch change is taking place.

Since there is no pitch change taking place, the internal gears 42 and44 both rotate anticlockwise at the same speed, and both carriers 52 and54 rotate clockwise at the same speed, whereby the pinions 48 and 50merely rotate anticlockwise on their axes at the same speed and rotatethe sun gears 46 and 41 clockwise faster than the hub ID.

If the worm 24 is now rotated one turn clockwise to increase the pitchof the blade 22, the internal gear 42 will gain part of ananti-clockwise turn on the internal gear 44. This part turn gain of gear42 causes the pinion 48 to gain approximately one anticlockwise turn onthe turns it would normally have made when no pitch change was takingplace.

Since the carrier 52 has a fixed one to one opposite rotation withrespect to gear 44,the one turn anticlockwise gain of the pinion 48causes a gain over the normal number of clockwise turns of the sun gear46, which in turn causes the carrier 54 to gain part of a. turn over itsnormal clockwise turns, whereby the pinion 58 is rotated anticlockwiseapproximately one turn with respect to the hub [0, which increases thepitch of the propeller l8.

A similar analysis of the directions of rotation will show that rotationof the worm 24 anticlockwise to decrease the pitch of the blade 22 willrotate theworm 20 clockwise to decrease the pitch of the blades [8,whether the propellers are then rotating or are stationary.

I claim:

1. In an aircraft propeller mechanism having two close-coupled, coaxial,tandem, contrarotating propeller hubs, one front hub and one rear hub,with a plurality of propeller blades in each hub having their rootsrotatable in bearings in said hubs, mechanism for drivably connectingsaid roots, whereby rotation of the roots of one propeller in onedirection rotates the roots of the other propeller in the otherdirection, said mechanism comprising, in combination, a front worm wheelon a front propeller-blade shank, a rear worm wheel on a rearpropeller-blade shank. a front worm in mesh with said front worm wheel,a rear worm in mesh with said rear worm wheel. a front-worm shaft, arear-worm shaft, front and rear worm shaft pinions on the front and rearworm shafts respectively, a planet pinion carrier freely rotatable onthe front hub, an external gear fast on said carrier and in mesh withthe front worm shaft pinion, a second planet pinion carrier fast on thefront hub, front and rear planet pinions on the first and second saidplanet pin ion carriers, respectively, a sun gear freely r0- tatable onsaid front hub and having a face width sufficient to mesh with both saidplanet pinions, an internally toothed gear fast on said rear hub and inmesh with the front planet pinion, a second internally toothed gearfreely rotatable on said rear hub and in mesh with the said secondplanet pinion, a second external gear fast on said second internal gearand in mesh with said rear worm shaft pinion, and means to rotate saidrear worm shaft.

2. In an aircraft propeller mechanism having two close-coupled, coaxial,contrarotating propeller hubs, one front hub and one rear hub, With aplurality of propeller blades in each hub, said blades having bladeshanks rotatable in bearings in said hubs, an improved mechanism fordrivably connecting said blade shanks, whereby rotation of the :bladeshanks of one propeller in one direction is coincident with rotation ofthe blade shanks of the other propeller in the other direction, saidmechanism comprising, in combination, a planet pinion carrier freelyrotatable on the front hub, an external gear fast on said carrier, asecond planet pinion carrier fast on the front hub, front and rearplanet pinions on the first and second said planet pinion carriersrespectively, a sun gear freely rotatable on said front hub and having aface width sufficient to mesh with both said planet pinions, aninternally toothed gear fast on said rear hub'and in mesh with the frontplanet pinion, a second internally toothed gear freely rotatable on saidrear hub and in mesh with the said rear planet pinion, a second externalgear fast on said second internal gear,,front speed reducing gearingconnecting the first said external gear to the blade shanks of the fronthub, rear speed reducing gearing connecting the second said externalgear to the blade shanks of the rear hub, and means to impart rotationto the rear speed reducing gearing.

3. In an aircraft propeller mechanism having two coaxial, tandem,contrarctatlng propeller hubs, one front hub and one rear hub, with aplurality of propeller blades in each hub said blades having their bladeshanks rotatable in hearings in said hubs, an improved mechanism fordrivably connecting said blade shanks, whereby rotation of the bladeshanks of one propeller in one direction is coincident with rotation ofthe blade shanks of the other propeller in the other direction, saidmechanism comprising, in com bination, a planet pinion carrier freelyrotatable on the front hub, an external gear fast on said carrier, asecond planet pinion carrier fast on the fronthub, front and rear planetpinions on the first and second said planet pinion carriers,respectively, a sun gear freely rotatable on said front hub and havingteeth adapted to mesh with both said planet pinions. an internallytoothed gear fast on said rear hub and in mesh with the front planetpinion, a second internally toothed gear freely rotatable on said rearhub and in mesh with the said rear planet pinion, a second external gearfast on said second internal gear, front gearing connecting the firstsaid external gear to the blade shanks of the front hub, rear gearingconnecting the second said external gear to the bladeshanks of the rearhub, and means including a portion of said rear gearing to impartrotation to the second said external gear.

4. In an aircraft mechanism having two close: coupled, contra-rotatingpropeller hubs, one front hub and on rear hub, with a plurality ofpropeller blades in each hub having blade shanks,

rotatable in bearings in said hubs, an improved mechanism for drivablyconnecting said blade shanks whereby causing rotation of the bladeshanks of one propeller in one direction causes rotation of the bladeshanks of the other propeller in the other direction, said mechanismcomprising, in combination, a planet pinion carrier freely rotatable onthe front hub, a second planet pinion carrier fast on the front hub,

front and rear planet pinions on the first and toothed gear freelyrotatable with respect to said rear hub and in mesh with the said rearplanet pinion, gearing connecting'the first said planet pinion carrierto the blade shanks of the front hub, a power receiving shaft, andgearing connecting the said second internally toothed gear to the bladeshanks of the rear hub and to the power receiving shaft.

5. In an aircraft propeller mechanism having two close-coupledcontrarotating propeller hubs,

, one front hub and one rear. hub, with a plurality of propeller bladesin each hub having blade shanks rotatably supported by said hubs, animproved mechanism for drivably connecting said blade shanks, wherebyrotation of the blade shanks of one propeller in one direction may nottake place except upon rotation of the blade shanks of theother'propeller in the other direction, said mechanism comprising, incombination, a planet pinion carrier rotatable freely about the axis ofsaid hubs, a coaxial planet pinion-carrier fast on said front hub, frontand rear planet pinions on the firstand second said planet pinioncarriers respectively, a sun gear element coaxial with said hubs andfreely rotatable with respect thereto and having. teeth in mesh withboth said planet pinions, an internal gear coaxial with and fast on saidrear hub and in mesh with said front planet pinion, a second.

internal gear coaxial with and freely rotatable with respect to saidhubs and in mesh with said rear planet pinion, rotation transmittingmeans connecting the first mentioned planet pinion car.- rier to theblade shanks of the front hub, a rotatable power input means androtation transmitrespect thereto and having teeth in mesh with both saidplanet pinions, an internal gear coaxial with and fast on said rear huband in mesh with said front planet pinion, a second internal gearcoaxial with and freely rotatable with respect to said hubs and in meshwith said rear ting means connecting the said second internal gear tothe blade shanks of the rear hub and to the rotatable power input means.

6. In a dual rotation propeller mechanism having close-coupled, coaxial,propeller hubs,

the axis of said hubs, a coaxial rear planet pinion carrier fast on saidfront hub, front and rear planet pinions on the front and rear. planetpinion carriers respectively, a sun gear element coaxialwith said hubsand freely rotatable with planet pinion, rotation transmitting meansconnecting the said front planet pinion carrier to the blade shanks ofthe front hub, rotation transmitting means connecting the said secondinternal gear to the blade shanks of the rear hub, and means to impartrotation to one of said rotation transmitting means.

7. In a dual rotation propeller mechanism having one front hub and onerear hub with a plurality of propeller blades in each hub having bladeshanks rotatably supported by said hubs, an improved mechanism for soconnecting said blade shanks to the same source of rotation thatrotation of the blade shanks of one propeller in one direction iscoincident with rotation of the blade shanks of the other propeller inthe other direction, said mechanism comprising, in combination, a frontplanet pinion carrier rotatable freely about the axis of said hubs, acoaxial rear planet pinion carrier fast on said front hub, front andrear planet pinions on the front and rear planet pinion carriersrespectively, a sun gear unit coaxial with said hubs and freelyrotatable with respect thereto and having teeth in mesh with both saidplanet pinions, an internal gear fast on said rear hub and in mesh withsaid front planet pinion, a second internal gear freely rotatablerelative to said hubs and in mesh with said rear planet pinion, meansdrivably connecting the said front planet pinion carrier tothe bladeshanks of the front hub, and means drivably connecting the said secondinternal gear tothe blade shanks of the rear hub. 8. For a dual rotationpropeller having one front and one rear hub with a plurality ofpropeller blades in each hub having blade shanks rotatably supported bysaid hubs, an improved gear mechanism for drivably connecting said bladeshanks for coincident rotation, said, gear mechanism comprising, incombination, a first planet pinion carrierv rotatable freely about theaxis of said hubs, a coaxial second planet pinion carrier fast on one ofsaid hubs, first and second planet pinions on the first and secondplanet pinions carriers respectively, a sun gear coaxial with said hubsand freely rotatable relative thereto and having teeth in mesh with bothsaid planet pinions, an internal gear coaxial with and fast on one ofsaid hubs and in mesh with said first planet pinion, a second internalgear coaxial with and freely rotatable relative to said hubs and in meshwith said second planet pinion,

means drivably connecting the said first planet ment, the front hub willrotate through a slightly greater angular movement.

HOWARD M. McCOY.

